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Biomedical subjects

J C Klein

Publications and source records attributed to J C Klein.

At least 37 records · Page 2Linked to original sources
PubMed1993

Cytokeratins expressed in experimental rat bronchial carcinomas.

Cytokeratin expression in rat lung tumors was studied using polypeptide-specific monoclonal antibodies (MAbs) to human cytokeratins 4, 5, 7, 8, 10, 13, 14, 18 and 19. Experiments were performed on tumor fragments derived from 5 experimental rat squamous-cell lung tumors and one adenocarcinoma, as well as on cell lines obtained from the same tumors. The aims of this study were to investigate the differentiation profile of the rat tumor tissue and established tumor cell lines based on light and electron microscopical features and on cytokeratin phenotype, to characterize the tumor type and degree of differentiation of the lung tumors maintained during passaging in experimental animals, and to compare the cytokeratin expression pattern in transplanted tumors with that of the cultures derived from these tumors. Our results indicate that, in general, the antibodies used cross-react with rat cytokeratins and that these MAbs can be used to phenotype rat lung carcinomas. Both the tumor fragments and the cultured cells revealed a similar pattern of cytokeratin expression. In addition, the degree of differentiation was maintained upon prolonged culturing in vitro. MAbs to cytokeratin sub-types can therefore be used to distinguish the main sub-types of rat lung tumors and can give an indication about the degree of differentiation.

Adenocarcinoma↗
PubMed1993

A glucose monitoring system for on line estimation in man of blood glucose concentration using a miniaturized glucose sensor implanted in the subcutaneous tissue and a wearable control unit.

We have developed a miniaturized glucose sensor which has been shown previously to function adequately when implanted in the subcutaneous tissue of rats and dogs. Following a glucose load, the sensor output increases, making it possible to calculate a sensitivity coefficient to glucose in vivo, and an extrapolated background current in the absence of glucose. These parameters are used for estimating at any time the apparent subcutaneous glucose concentration from the current. In the previous studies, this calibration was performed a posteriori, on the basis of the retrospective analysis of the changes in blood glucose and in the current generated by the sensor. However, for clinical application of the system, an on line estimation of glucose concentration would be necessary. Thus, this study was undertaken in order to assess the possibility of calibrating the sensor in real time, using a novel calibration procedure and a monitoring unit which was specifically designed for this purpose. This electronic device is able to measure, to filter and to store the current. During an oral glucose challenge, when a stable current is reached, it is possible to feed the unit with two different values of blood glucose and their corresponding times. The unit calculates the in vivo parameters, transforms every single value of current into an estimation of the glucose concentration, and then displays this estimation. In this study, 11 sensors were investigated of which two did not respond to glucose. In the other nine trials, the volunteers were asked to record every 30 s what appeared on the display during the secondary decrease in blood glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Repair and replication of plasmids with site-specific 8-oxodG and 8-AAFdG residues in normal and repair-deficient human cells.

The in vivo mutagenicity of 7-hydro-8-oxo-2'-deoxyguanosine (8-oxodG) and N-(guanin-8-yl)-N-acetyl-2-aminofluorene (8-AAFdG) in human cells was determined by transfecting various cell lines with plasmids that carried a single adduct at a defined site. 8-OxodG is one of the many DNA modifications formed by oxygen radicals, and was found to be highly miscoding during replication with purified DNA polymerases in vitro. Here we show that the frequency of mutations induced by 8-oxodG during replication in vivo is at most only 2% above background. The most predominant mutation found was a single G----T transversion. The frequency of this transversion was found to be 3 to 5-fold increased in excision repair deficient XP-A cells. Interestingly, also the replication of 8-oxodG containing plasmids was significantly impaired (approximately 4-fold) in the XP-A cells, but not in HeLa cells, normal fibroblasts or XP-A revertant cells. When 8-AAFdG containing plasmids were used, the mutation frequencies did not exceed background levels (less than 2%) with any of the cell lines tested. The presence of 8-AAFdG almost completely inhibited plasmid replication (more than 50-fold) in XP-A cells. Apparently, both 8-AAFdG and 8-oxodG are not or poorly repaired in these cells, causing a block of DNA replication. This suggests that both lesions are substrates for excision repair, although to a varying extent.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1992

Progress toward the development of an implantable sensor for glucose.

The development of an electrochemically based implantable sensor for glucose is described. The sensor is needle-shaped, about the size of a 28-gauge needle. It is flexible and must be implanted subcutaneously by using a 21-gauge catheter, which is then removed. When combined with a monitoring unit, this device, based on the glucose oxidase-catalyzed oxidation of glucose, reliably monitors glucose concentrations for as long as 10 days in rats. Various design considerations, including the decision to monitor the hydrogen peroxide produced in the enzymatic reaction, are discussed. Glucose constitutes the most important future target analyte for continuous monitoring, but the basic methodology developed for glucose could be applied to several other analytes such as lactate or ascorbate. The success in implementation of such a device depends on a reaction of the tissue surrounding the implant so as not to interfere with the proper functioning of the sensor. Histochemical evidence indicates that the tissue response leads to enhanced sensor performance.

Biocompatible Materials↗
PubMed1990

Use of shuttle vectors to study the molecular processing of defined carcinogen-induced DNA damage: mutagenicity of single O4-ethylthymine adducts in HeLa cells.

We developed a simian virus 40 based shuttle vector system to study the molecular consequences of distinct carcinogen-induced DNA lesions in human cells. To establish the mutagenicity of O4-ethylthymine adducts, oligonucleotides carrying a single O4-ethylthymine adduct at a unique position were ligated into the vector molecules. Following replication in HeLa cells on average 23% of the progeny molecules carried a mutation in the region of modification. The vast majority of these mutations represented single T----C transitions at the position of the modified base, most probably as a consequence of mispairing of the O4-ethylthymine residues during replication. To a minor extent the O4-ethylthymine adduct may also induce T----A transversions or double point mutations. The in vivo mutation frequency of the adduct was found to be comparable to that of a C-A mismatch at the same position, but was lower than that expected from in vitro experiments with adducted DNA templates and purified DNA polymerases.

Base Sequence↗
PubMed1987

Differential behavior of human bronchial carcinoma cells in culture.

A feeder layer culture system suited to grow carcinoma cells derived from solid human lung tumors was developed. This report deals with culturing of the four main histological types of lung carcinomas observed in 37 patients: 19 squamous cell, 6 adenocarcinomas, 7 small cell, and 5 large cell carcinomas. The cultures were initiated from 24 fresh human surgical specimens and from 14 human lung tumors grown as xenografts in nude mice. Three different patterns of behavior in culture were found to be characteristic for squamous cell, adenocarcinomas, and small cell carcinomas, respectively. The culture pattern presented by the primary cultures did not appreciably change after passaging in vitro for periods of up to 2 years, even after infinite cell lines were established. Cultures of large cell carcinoma showed one or more of these patterns. From these patterns cells could be cloned and subsequently cultured as separate stable lines. The system described facilitates the identification of specific types of human lung carcinomas almost immediately (within 1 h) after plating (Phase I) as well as during culture.

Adenocarcinoma↗
PubMed1987

A rapid and simple hapten conjugation method for monoclonal antibodies to be used in immunoenzyme single and double staining procedures.

A rapid and simple method was developed for the haptenization of monoclonal antibodies (MAbs), to be used in immunoenzyme single and double staining techniques. Using this method minute amounts of MAbs can be haptenized without purification of the antibody or removal of the excess hapten. The haptenized MAb can be ready for use with 2.5 h. The method consists of a direct incubation of the antibody with the haptenizing agent and subsequent addition of an amino acid solution to stop the reaction. Commonly available reagents were tested, of which dinitrofluorobenzene, trinitrobenzene sulfonic acid and an oxazolone derivative gave the best results. The procedure was evaluated by using MAbs directed against lymphoid cell surface membrane antigens in an indirect immunoenzyme staining on frozen sections using peroxidase or alkaline phosphatase-conjugated anti-hapten antibodies as second step antibody. It was found that those MAbs, which show good staining results in conventional indirect immunoenzyme procedures, can also be used successfully after haptenization in single as well as double staining procedures. Combination of haptenized and biotynilated MAbs gave good results when weakly reactive MAbs had to be included in immunoenzyme double staining.

Antibodies, Monoclonal↗
PubMed1986

Nasal respiratory function and craniofacial growth.

Nasal respiratory function and its relationship to growth development of the craniofacial structure has been a subject of interest and controversy for over 100 years. The otolaryngologist as the primary physician with responsibility of managing the upper respiratory tract is obviously most intimately involved with diagnosis and treatment of upper respiratory tract problems. To further evaluate the evidence regarding causes of craniofacial growth, a study was done involving pretreatment orthodontic subjects and their manifestation of classic signs of adenoid facies ("long-face syndrome"). Randomly selected were 106 subjects, ranging in age from 6 to 13 years, for evaluation of the facial features and medical history associated with long-face syndrome. No conclusive proof was found that nasal respiratory obstruction alters facial growth development. Studies of the nasal respiratory function need to be done utilizing clear definitions of respiratory mode and objective; reproducible techniques of measuring respiratory modes must be employed. Highly selected orthodontic patients can benefit from adenoidectomy and/or tonsillectomy.

Adolescent↗
PubMed1984

Automatic detection of microaneurysms in diabetic fluorescein angiography.

A computerized method for the detection of microaneurysms (MA) in fluorescein angiograms is proposed, using the concepts of mathematical morphology. The MA which are almost circular particles, are extracted from the image by performing different "top-hat transformations". Some particles, however, may then be detected inside the nonhomogeneous vessels, and it is necessary to be able to extract the vasculary net. The MA which present fuzzy boundaries (due to the leakage of fluorescein) are the most difficult to extract. The algorithm has been tested on 25 angiograms, with 1 045 MA analysed. A comparison between the automatic counting procedure and three manual methods of counting has been made to prove the robustness of the proposed method.

Aneurysm↗
PubMed1982

Metformin reduces post-prandial insulin needs in type I (insulin-dependent) diabetic patients: assessment by the artificial pancreas.

It has been suggested that biguanides should be used in Type 1 (insulin-dependent) diabetic patients in order to diminish insulin requirements and reduce the chances of insulin reactions. The efficacy of these compounds in such patients has been controversial. We have studied the effect of metformin (850 mg) given at 08.00 h in diminishing insulin needs after a 60 g carbohydrate mixed meal taken at 12.00 h, using an artificial pancreas and a sequential analysis of the results. The morning test dose of metformin or placebo was preceded by 48 h treatment with metformin (850 mg twice daily) or placebo. After the eighth patient a 26% saving of insulin need was demonstrated in the metformin-treated group (p less than 0.01). Metformin is thus effective in reducing post-prandial insulin needs in Type 1 diabetic patients, although its use in such circumstances requires consideration of several other issues.

Adult↗
PubMed1981

Correlation between the nature and amount of carbohydrate in meal intake and insulin delivery by the artificial pancreas in 24 insulin-dependent diabetics.

We have studied the effects of mixed meals and dextrose intake on blood glucose and insulin delivery by the artificial pancreas in 24 insulin-dependent diabetics. A group of 12 patients had 3 mixed meals containing at random 20, 40, and 60 g of complex carbohydrate along with protein and fat; another group of 12 diabetics, comparable in weight, age, and duration of diabetes, received at random 20, 40, and 60 g of dextrose. Dextrose ingestion led to a higher initial blood glucose increase than did the mixed meal, but the duration of blood glucose increase lasted significantly longer after the mixed meal than after the dextrose load. The areas under the curves of hyperglycemia were not significantly different. There was a high (but not linear) correlation between the total amount of insulin delivered in order to restore initial blood glucose values and the amount of CHO consumed. There was no correlation with age, body weight, duration of diabetes, nor with the nature and order of administration of the CHO load; 5.1 +/- 1.6 to 13.7 +/- 2.1 units of insulin were needed for a period of 94 +/- 11 to 132 +/- 11 min. It is suggested that some of the data obtained in this study might be useful in the programming of an open-loop insulin infusion system.

Adult↗
PubMed1981

How selective are agar cultures for malignant transformation?

In vitro assays that permit cloning of tumour cells in soft agar have been improved during the last 5 years. Two of them (2, 10) are claimed to be useful as test systems for the screening of new anticancer drugs and even for drug sensitivity testing of individual human tumours in the devicing of individualized cancer chemotherapy regimens. Three assays were investigated for this report: those of Toshio Kuroki (TK) (11) and Hamburger and Salmon (HS) (5, 10) and that in use for bone marrow cell cultures (BM) (3). Cells of various origins were tested for their growth capacity and colony formation in these three assays. Included were cells of 10 established lines classified as malignant or nonmalignant according to the in vivo malignancy test (6). Cells freshly derived from two tumours ans those from five tumours after 2-10 passages in monolayer culture were also used as test cells. The BM assay gave the best results. Up to now, a 100 per cent correlation has been found between the in vivo and in vitro test. Investigations are under way to determine whether this assay can also be used as a transformation assay using cells with a low transformation rate.

Agar↗
PubMed1980

A sophisticated programmable miniaturised pump for insulin delivery.

We have conceived a truly pre-programmable infusion system usable for intravenous administration of insulin in diabetic subjects. The original system has been built into a small, commercially available, syringe-pump of which only the case and the mechanical parts have been kept. The computing until has a timer, a programmable memory of 512 words by 8 bits and a digital-to-frequency converter to run the motor which drives the syringe. The memory contains 8 profiles of insulin injections stored in digital form over 64 words. Each profile is selected by the patient before eating according to the carbohydrate content of the planned meal and last about two hours, starting from and returning to the basal rate of insulin, at which it remains until next profile selection. Amount, profiles and duration of insulin injection are either mean values deduced from previous studies with a closed-loop artificial pancreas or personally fitted values; they are stored in an instantly replaceable memory cell. This device allows the patient to choose the time, nature and amount of his food intake.

Computers↗